Re-treatment for ophthalmic correction of refraction

ABSTRACT

A planning device generating control data for a treatment apparatus for refraction-correcting ophthalmic surgery is provided, said apparatus using a laser device to separate a corneal volume, which is to be removed for correction, from the surrounding cornea by at least one cut surface in the cornea of an eye, said planning device comprising an interface for receiving corneal data including information on pre-operative cuts which were generated in a previous ophthalmic operation, and computing means for defining a corneal cut surface which confines the corneal volume to be removed, said computing means defining the corneal cut surface on the basis of the corneal data and generating a control dataset for the corneal cut surface for control of the laser device.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 15/853,037, filed Dec. 22, 2017, which is a continuation of U.S.patent application Ser. No. 14/978,992, filed Dec. 22, 2015, now U.S.Pat. No. 9,855,170, issued Jan. 2, 2018, which is a continuation of U.S.patent application Ser. No. 14/135,695, filed Dec. 20, 2013, now U.S.Pat. No. 9,237,965, issued Jan. 19, 2016, which is a divisional of U.S.patent application Ser. No. 12/109,921, filed Apr. 25, 2008, now U.S.Pat. No. 8,623,038, issued Jan. 7, 2014, which claims the benefit ofU.S. Provisional Application No. 60/914,179, filed Apr. 26, 2007, all ofwhich are incorporated herein in their entirety by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention relates to a planning device generating control data for atreatment apparatus for refraction-correcting ophthalmic surgery, saidapparatus using a laser device to separate a corneal volume, which is tobe removed for correction, from the surrounding cornea by at least onecut surface in the cornea. The invention further relates to a treatmentapparatus for refraction-correcting ophthalmic surgery, said apparatuscomprising a planning device of the aforementioned type.

The invention further relates to a method of generating control data fora treatment apparatus for refraction-correcting ophthalmic surgery,which apparatus uses a laser device to separate a corneal volume, whichis to be removed for correction, from the surrounding cornea by at leastone cut surface in the cornea.

Finally, the invention also relates to a method forrefraction-correcting ophthalmic surgery, wherein a corneal volume,which is to be removed for correction, is separated from the surroundingcornea by at least one cut surface formed in the cornea by a treatmentapparatus comprising a laser device.

2. Background

In the prior art, the most diverse treatment methods aiming to correctrefraction of the human eye are known. The aim of said surgical methodsis to selectively modify the cornea so as to influence the refraction oflight. Various surgical methods are employed for this purpose. The mostcommon method is presently the so-called laser in situ keratomileusis,also abbreviated as LASIK, wherein a corneal lamella is first detachedon one side and folded aside. The detachment of said lamella can also beeffected using a mechanical microkeratome or a so-called laser keratomeas distributed, for example, by Intralase Corp., Irvine, USA. Once thelamella has been detached and folded aside, the LASIK operation providesfor the use of an excimer laser which ablates the corneal tissue thusexposed under the lamella. After a volume located beneath the cornealsurface has been evaporated in this manner, the corneal lamella isfolded back in its original place.

The application of a laser keratome for exposing the lamella isadvantageous as compared to a mechanical knife, because it reduces therisk of infection while improving the cut quality. In particular, thelamella may be produced with a much more constant thickness if laserradiation is used. Also, the cut is generally smoother, which reducesthe risk of subsequent optical impediments by this boundary surfacewhich still remains after surgery. However, this method has thedisadvantage of requiring the use of two different treatmentapparatuses, namely the laser keratome for exposing the lamella, on theone hand, and the laser evaporating the corneal tissue, on the otherhand.

These disadvantages are overcome by a method recently implemented byCarl Zeiss Meditec AG and abbreviated by the term FLEX. In this method,a femtosecond laser is used to form such a cut geometry in the corneathat a corneal volume (a so-called lenticle) is separated within thecornea. This corneal volume is then removed manually by the surgeon. Theadvantage of this method is, on the one hand, that the cut quality isfurther improved by the use of the femtosecond laser. On the other hand,only one treatment apparatus is required because the excimer laser is nolonger employed. When generating cut surfaces in the cornea by laserradiation, the optical radiation effect is usually taken advantage of togenerate an optical breakthrough. It is also known to introduceindividual pulses, whose energy is below a threshold value for anoptical breakthrough, into the tissue or the material in a superimposedmanner such that a separation of material or tissue is also achievedthereby. This concept of cut generation in the corneal tissue allows agreat variety of cuts.

The result of treatment remaining in these described laser-surgicalmethods is a cut in the cornea, and although it is no longer visible tothe naked eye after a short time, it never heals due to the particularnature of the cornea, because the cornea is “dead” tissue in thisrespect. Due to the cut, the parts of tissue above the cut are no longerfixedly connected to the parts of tissue below the cut.

However, a need for re-treatments may arise, namely if either the resultof the previous operation is not yet satisfactory in terms of thecorrection of refraction, or if the previous operation was notsufficiently completed for any reason (e.g. due to termination of theoperation).

In the case of an insufficient refractive correction, it is known forthe excimer laser-based LASIK operation to lift off the corneal lamellaagain and to remove additional corneal tissue for re-treatment.

However, this approach is impractical for the FLEX method, because itwould not allow a re-treatment to be carried out by the same device asfor the previous operation, so that it would be mandatory to keep anextra device ready merely for re-treatments.

For terminated laser-based FLEX operations, in fact, no useful or safesolution is known at all.

SUMMARY OF THE INVENTION

Therefore, it is an object of the invention to provide a planning devicefor generating control data, a treatment apparatus forrefraction-correcting ophthalmic surgery, as well as a method ofgenerating control data for such treatment apparatus or a method forrefraction-correcting ophthalmic surgery, which simply enablesre-treatment without ablation of corneal tissue or continuation of aterminated treatment, respectively.

According to the invention, this object is achieved by a planning deviceof the above-mentioned type. The planning device comprises an interfacefor receiving corneal data including information on pre-operative cutswhich were generated in a previous ophthalmic operation and computingmeans for defining a corneal cut surface. The computing means confinesthe corneal volume to be removed and defines the corneal cut surface onthe basis of the corneal data, then generates a corneal cut surfacecontrol dataset for control of the laser device.

The object is further achieved by a treatment apparatus forrefraction-correcting ophthalmic surgery. This treatment apparatuscomprises an interface, a laser device, and a planning device. Theinterface supplies the corneal data including information onpre-operative cuts which were generated in a previous ophthalmicsurgery. The laser device separates a corneal volume, which is to beremoved, from the surrounding cornea by at least one cut surface formedin the cornea by laser radiation according to control data. The planningdevice may be of the type just mentioned, which generates the controldata.

The object is finally also achieved by a method of generating controldata according to the above-mentioned type, said method comprising:accessing corneal data, which include information on pre-operative cutsgenerated in a previous ophthalmic operation; defining a corneal cutsurface, which confines the corneal volume to be removed, on the basisof the corneal data, and generating a control dataset for the cornealcut surface for control of the laser device.

Finally, the object is also achieved by a method ofrefraction-correcting ophthalmic surgery, which comprises: accessingcorneal data, which include information on pre-operative cuts generatedin a previous ophthalmic operation; defining a corneal cut surface,which confines the corneal volume to be removed, on the basis of thecorneal data, and generating a control dataset for the corneal cutsurface; transmitting the control data to the treatment apparatus, andgenerating the cut surfaces by control of the laser device using thecontrol dataset.

The object is further achieved by the use of a treatment apparatus for arefraction-correcting ophthalmic operation, said treatment apparatuscomprising a laser device, which forms a cut surface in cornea by pulsedlaser radiation in order to isolate in the cornea a corneal volume whichis to be removed for correction, said ophthalmic operation beingeffected as a re-treatment of a previous operation which left cuts inthe cornea.

Because the inventors realized that such an apparatus can be applied ina surprisingly unproblematic manner to cases in which cuts have alreadybeen made pre-operatively in the cornea, this concept provides for are-treatment using an apparatus known for the FLEX method.

Thus, the invention quite generally provides for generating at least oneadditional cut surface in the cornea, which cut surface isolates acorneal volume whose removal results in the desired refractivecorrection. In the state of the art, such corneal volume is alsoreferred to as a lenticle, because it is lenticular in most cases.

By taking into consideration the pre-operative cuts, i.e., those cutsalready existing as a result of the previous operation, a re-treatmentcan now be carried out both in cases where a residual correction ofrefraction is still required and in cases where the previous operationwas not duly completed, i.e., terminated. Particularly in the lattercases, there has been no suitable means whatsoever in the prior art toachieve a correction of refraction by an ophthalmic method.

A re-treatment is advantageously carried out such that the corneal cutsurface defined by the planning device, by the planning method, thecorneal cut surface generated by the treatment apparatus, or thetreatment method does not intersect the pre-operative cuts. This has theadvantage of avoiding any undesired isolation of volumes in the corneawhich are possibly removed from the cornea along with the removal of theactually intended volume and lead to an unpredictable alteration of thecorneal surface. Further, this also avoids undesired weakening whenfolding aside the lamella isolated during re-treatment or undesiredfolding aside of further parts of the cornea, in a manner not intended,which folding could occur due to an insufficiently consideredpre-operative cut.

Such negative occurrences during re-treatment can be avoided in aparticularly reliable manner if the computing means of the planningdevice or the corresponding planning method, respectively, define thecut surface in the cornea such that the corneal volume to be removed islocated completely posterior to the pre-operative cuts generated,completely anterior to the pre-operative cuts, or encloses thepre-operatively generated cuts.

The first or second variant are particularly suitable in cases where theprevious operation went according to plan, but a residual eyesightdefect still has to be corrected. The third variant is suitable in caseswhere the previous operation—for whatever reasons—was terminated,because the remaining pre-operative cuts, whose position may possiblynot be determined with absolute precision, are removed from the corneawhen removing the corneal volume isolated by the re-treatment.

On the other hand, if the position of the pre-operative cuts is, or canbe determined, with sufficient precision, an alternative of theinvention allows the corneal cut surface to be defined as a continuationof the pre-operative cuts.

Because the existing pre-operative cuts have to be taken intoconsideration, the planning of the corneal cut surface is of particularimportance in the case of a re-treatment. This planning is facilitatedfor the surgeon if a display device for visual representation of thecornea and of the existing pre-operative cuts, preferably in asuperimposed representation, is provided.

It is a particular advantage that specific data can be used for planningand execution of the re-treatment. These may be data of the previousoperation, which are stored in the apparatus; diagnostic data of the eyeto be treated, which were acquired after the previous operation andprior to the re-treatment; or data of the eye to be treated, which wereacquired intra-operatively, i.e. during re-treatment. Advantageously,such corneal data can be generated on the basis of a measurement of theeye and can be supplied to the planning device, in which case ameasurement device is used which optionally comprises one or more of thefollowing devices: autorefractor, refractometer, keratometer,aberrometer, wavefront measurement device, OCT, confocal cornealmicroscopy, Scheimpflug camera, and topographic measurement.

If a re-treatment is carried out due to a residual need for correction,i.e. if the previous operation was completed according to plan, aparticularly important detail is, of course, the eyesight defect to becorrected and/or the thickness and/or diameter of a pre-operativelygenerated corneal lamella which can be folded aside.

A re-treatment can be carried out more easily or precisely when accurateknowledge of the pre-operatively existing cut is available. Therefore,it is advantageous, quite generally and independently of the realizationof the re-treatment, if a laser-surgical treatment apparatus forrefractive ophthalmic surgery comprises a device which logs the progressof the generated cuts during an operation. If the treatment apparatususes pulsed laser radiation, said logging may include the position andthe energy of each laser radiation pulse focused into the cornea. Therelative position of the cornea (or the eye, respectively) and of theapparatus is also logged. Such logging is unknown in the prior art. Infact, such logging goes far beyond the usual extent of availableinformation which comprises information on the patient, the need forcorrection of refraction and, at best, the cut surface geometry used.Accordingly, the data storage volume is advantageous, even thoughconsiderable in volume, when a re-treatment is required, especially ifthe previous operation was not completed. If so, simple and precisecontinuation of the terminated cut surface generation is then possible.

For re-treatment, the invention provides for the defined or used cutsurfaces to be geometrically arranged such that either no intersectionoccurs at all with the pre-operative, already existing cut or that thiscut is suitably supplemented or continued.

Several cases are distinguished. In the case of a subsequent refractivecorrection by which the previous method is duly completed, theadditional cuts can be arranged such that they are located less deeplybelow the corneal surface than the pre-operatively existing cut whichwas generated to fold the corneal lamella aside. As an alternative, itis possible to arrange the corneal cut surface at a greater depth thanthe pre-operatively existing cut. The lenticle to be removed is thenremoved from a corneal region which is located below the pre-operativelygenerated corneal lamella. By contrast, the lenticle may be locatedwithin the corneal lamella in the first-mentioned case.

These variants, as with the variant in which the corneal volume enclosesthe pre-operatively existing cut, are based on the concept that thecorneal volume to be removed, usually in the shape of a lenticle, isgenerated without re-using the pre-operative cuts, e.g. by a separateflap cut as well as a separate lenticle cut.

As an alternative, it is possible to use the already existingpre-operative cut and to define the corneal cut surface such that thecorneal cut surfaces supplement or utilize the pre-operative cut whenisolating the corneal volume to be removed by re-treatment. The lenticleis then limited by the pre-operatively existing cut as well as by thedefined corneal cut surface. Cut surfaces are thus generated morequickly. However, this protocol requires precise knowledge of thepre-operative cut. Supplementing may accordingly be effected above thepre-operative cut, i.e. through the corneal lamella or below thepre-operative cut, i.e. towards the inner surface of the cornea.

In the case of a re-treatment preceded by a previous operation that wasnot completed, there is always the problem that, depending on how thepre-operative cut was generated, there may exist only incomplete cutsurfaces. For example, a lenticle cut intended to posteriorly limit thecorneal volume that should have been removed by the previous operationmay have been carried out completely or partially. However, there maypossibly be also a partial or even nearly complete flap cut which wasintended to limit the lenticle anteriorly. There may also be a case inwhich the peripheral cut, which allows the corneal lamella to be foldedaside, is the only cut which has not been completed. In each case, it isoften adequate to continue these cuts if the pre-operatively generatedcuts are precisely known. The continuation may also be such that the cutsurface includes part of the pre-operative cut already generated, i.e.generating the re-treatment cut surface is begun in a region in which apre-operative cut is already expected. An overlap ensures continuousseparation of tissue by the combined effect of the pre-operative cut andof the cut surface generated during re-treatment. If it is not desiredto continue the pre-operative cuts, e.g. because their positions are notsufficiently precisely known or the quality of these cuts is notsatisfactory, the cut surface for isolation of the corneal volume to beremoved is often conveniently defined such that it is either completelyanterior to the pre-operative cuts, completely posterior to thepre-operative cuts, or confines the pre-operative cuts in the cornealvolume to be removed.

As the discussion of the re-treatment shows, it may be important todetermine the position of the pre-operative cut in order to position thecorneal cut surfaces as exactly as possible. Alternatively,

1. The position of the pre-operative cut is measured by diagnosticmethods prior to carrying out the re-treatment. The diagnostic methodsmay comprise confocal microscopy of the cornea, optical coherencetomography, or the use of a slit lamp with a measurement cameraconnected thereto.

2. Position data of the pre-operative cuts can be derived from internaldata from the apparatus by which the previous operation was conducted.Thus, in planning the re-treatment, input data used to plan the previousoperation and/or data acquired during execution of the previousoperation may be used. Examples of data which can be acquired duringexecution of the previous operation include: data from anintra-operative measurement of the residual stroma thickness, dataconcerning the time at which the operation was terminated and/or dataconcerning the real position of the cuts generated by the previousoperation.

3. Position data concerning the pre-operatively generated cuts duringthe re-treatment can also be determined by a measurement system providedin the apparatus for the re-treatment. Stated otherwise, the positiondata concerning the pre-operatively existing cuts may beintraoperatively determined. Such a measurement system may use aconfocal sensor or optical principles of coherence tomography. It isalso possible to execute a test cut using the treatment apparatus and toderive the position of the pre-operatively existing cut from the data ofan observation camera.

Describing the position of the pre-operatively existing cut generallyrequires the complete indication of the function z(x,y) for all pairs ofcoordinates (x,y) of the cut area. However, a considerable reduction ofparameters is possible, e.g. for a circular flap of homogeneousthickness. In this case, it is sufficient to determine flap thickness,flap diameter, and the position of the flap's center.

During execution of a laser-surgical operation carried out using pulsedlaser radiation, the position of the laser focus follows a previouslycomputed trajectory {right arrow over (s)}(t):=R¹→R³ , with t∈I=[0,T]⊂R, for the purpose of generating a two-dimensional cut surfaceS:=R²→R³. R is the quantity of real numbers and R^(n) is the n^(th)dimension Euclidian vector space. Individual partial cut surfacesS_(j)⊂S are sequentially represented by {right arrow over (s)}(t), i.e.for each partial cut surface S_(j), there is exactly one intervalI_(j)=[t₁, t₂]_(j) from which the trajectory {right arrow over (s)}(t)of S_(j) comes. Due to the strict sequencing of the cut surfaces S_(j)in the trajectory {right arrow over (s)}(t), the individual intervalsare disjoint, i.e.

∃!I _(j) ⊂I|∀t∈I _(j)|{right arrow over (s)}(t)∈S _(j) {circumflex over( )}∀i≠j|I _(i) ∩I _(j)=Ø

holds true.

The trajectory {right arrow over (s)}(t) can be computed, for a specificlaser therapy, together with the corresponding set of disjoint intervalsI_(j). During laser therapy, the parameter t passes through the intervalI=[0,T]. The therapy is complete as soon as t=T or at least

$\left. {\forall{k \in {\bigcup\limits_{j}I_{j}}}} \middle| {t \geq {k.}} \right.$

If the therapy is terminated at t=t_(int), the intervals I_(j) determineat which cut surface the termination took place, or how far this cutsurface has been completed. A partial cut surface S_(j) is complete when∀k∈I_(j)|k≤t_(int) holds true. Thus, in order to determine the locationwhere the therapy was terminated, it is sufficient to determine the timeat which it was terminated. It is possible here to determine the timewithin a certain tolerance, i.e. for example at a resolution of 1% of T.

Determining the termination time makes logging easier and safer.Therefore, it is advantageous to simplify logging such that it does notinvolve logging the position of each laser radiation pulse emitted intothe cornea, but merely the logging of parameters of the emission oflaser radiation pulses (e.g. frequency of the pulses), of focusdeflection (e.g. deflection speed), as well as indicating the exact timeof any termination of the operation and cut geometry data.

It is not decisive for the invention how the pre-operative cuts weregenerated. Thus, in principle, they may also have been generated using amechanical microkeratome or the like.

It will be appreciated that the above-mentioned features and those yetto be explained below can be employed not only in the combinationsindicated, but also in other combinations or alone, without departingfrom the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail below with reference tothe enclosed drawings, which also disclose features essential to theinvention and wherein:

FIG. 1 shows a schematic representation of a treatment apparatuscomprising a planning device for a re-treatment in connection withophthalmic correction of refraction;

FIG. 2 shows a schematic representation of the effect of the laserradiation used in the treatment apparatus of FIG. 1;

FIG. 3 shows a further schematic representation of the treatmentapparatus of FIG. 1 with respect to the introduction of the laserradiation;

FIG. 4 shows a schematic sectional view of the cornea, illustrating theremoval of the corneal volume in connection with the ophthalmiccorrection of refraction;

FIG. 5 shows a schematic representation relating to the construction ofthe treatment apparatus of FIG. 1 with particular reference to theplanning device present;

FIG. 6 shows a schematic sectional view of the cornea in connection withthe ophthalmic correction of refraction in a re-treatment for correctionof a residual eyesight defect;

FIG. 7 shows a schematic sectional view of the cornea in connection withthe ophthalmic correction of refraction in a re-treatment forcontinuation of a terminated previous operation;

FIG. 8 shows a further schematic sectional view of the cornea inconnection with the ophthalmic correction of refraction in are-treatment for continuation of a terminated previous operation bycontinuing the existing cut surface; and

FIG. 9 shows a further schematic sectional view of the cornea inconnection with the ophthalmic correction of refraction in are-treatment for correction of a residual eyesight defect, using theexisting cut surface.

DETAILED DESCRIPTION

A treatment apparatus for ophthalmic correction of refraction is shownin FIG. 1 and generally indicated at 1. The treatment apparatus 1 isprovided for re-treating correction of refraction to the eye 2 of apatient 3. For this purpose, the treatment apparatus 1 comprises a laserdevice 4, which emits a laser beam 6 from a laser source 5, said beambeing directed as a focused beam 7 into the eye 2 or into the cornea.The laser beam 6 is preferably a pulsed laser beam having a wavelengthof between 400 nanometers and 10 micrometers. Further, the pulseduration of the laser beam 6 is in the range of between 1 femtosecondand 10 picoseconds, with pulse repetition frequencies of from 1 to 1000kilohertz and pulse energies of between 0.01 microjoules and 0.01millijoules being possible. Thus, the treatment apparatus 1 generates acut surface in the cornea of the eye 2 by deflection of the pulsed laserradiation. For this purpose, the laser device 4 or its laser source 5,respectively, also includes a scanner 8 as well as a radiation intensitymodulator 9.

The patient 3 is lying on a table 10, which is shiftable in threespatial directions in order to align the position of the eye 2 with theincidence of the laser beam 6. In a preferred construction, the table 10is shiftable by a motor drive.

Control may be effected, in particular, by a control device 11, whichgenerally controls the operation of the treatment apparatus 1 and isconnected to the treatment apparatus via suitable data links, forexample connecting lines 12, for this purpose. This communication may,of course, be effected also via other paths, e.g. by light guides or byradio. The control device 11 performs the corresponding settings, timecontrol of the treatment apparatus 1, in particular of the laser device4, and thus performs corresponding functions of the treatment apparatus1.

The treatment apparatus 1 further comprises a fixing device 15 whichpositionally fixes the cornea of the eye 2 with respect to the laserdevice 4. This fixing device 15 may comprise a known contact glass 45with which the cornea is placed in contact by a vacuum and which impartsa desired geometrical shape to the cornea. The person skilled in the artis familiar with such contact glasses from the prior art, for examplefrom DE 102005040338 A1. The disclosure of this document is fullyincorporated herein by reference as far as the description of aconstruction of the contact glass 45 usable for the treatment apparatus1 is concerned.

The control device 11 of the treatment apparatus 1 further comprises aplanning device 16, which will be explained in more detail below.

FIG. 2 schematically shows the effect of the incident laser beam 6. Thelaser beam 6 is focused and is incident in the cornea 17 of the eye 2 asthe focused laser beam 7. Schematically indicated optics 18 are providedfor focusing. They effect a focus in the cornea 17, in which focus thelaser radiation energy density is so high that, in combination with thepulse duration of the pulsed laser radiation 6, a non-linear effectappears in the cornea 17. For example, each pulse of the pulsed laserradiation 6 in the focus 19 may produce an optical breakthrough in thecornea 17, which in turn initiates a plasma bubble indicated onlyschematically in FIG. 2. When the plasma bubble forms, the tissue layerseparation comprises an area larger than the focus 19, although theconditions for producing the optical breakthrough are achieved only inthe focus 19. In order for an optical breakthrough to be generated byeach laser pulse, the energy density, i.e. the fluence of the laserradiation, must be above a certain pulse duration-dependent thresholdvalue. This connection is known to the person skilled in the art, forexample, from DE 69500997 T2. Alternatively, a tissue-separating effectcan also be achieved by pulsed laser radiation in that several laserbeam radiation pulses are emitted in a region where the focus spotsoverlap. In this case, several laser radiation pulses cooperate toachieve a tissue-separating effect.

However, the type of tissue separation used by the treatment apparatus 1is not really relevant to the following description; it is onlyessential that a cut surface is generated in the cornea 17 of the eye 2.

Now, in order to perform an ophthalmic correction of refraction, acorneal volume is removed from a region within the cornea 17 by means ofthe laser radiation 6, separating tissue layers therein which isolatethe corneal volume and enable the removal of the latter then. Forisolation of the corneal volume to be removed, the position of the focus17 of the focused laser radiation 7 in the cornea 17 is shifted, forexample in cases where pulsed laser radiation is introduced. This isschematically shown in FIG. 3. The refractive properties of the cornea17 are selectively modified by removal of the volume so as to achievethe correction of refraction. Therefore, said volume is lenticular inmost cases and is referred to as a lenticle. The removal of the cornealvolume is effected here as a re-treatment. It was either preceded by anophthalmic correction of refraction, which left a residual need forcorrection, or is even an ophthalmic correction of refraction terminatedduring the operation, wherein the cut surfaces were generatedincompletely. Of course, this also creates a need for correction.

FIG. 3 shows the elements of the treatment apparatus 1 only insofar asthey are required in order to understand how the cut surfaces areproduced. As already mentioned, the laser beam 6 is bundled in a focus19 in the cornea 17, and the position of the focus 19 in the cornea isshifted such that focused energy from laser radiation pulses isintroduced into the tissue of the cornea 17 at different locations so asto produce cut surfaces. The laser radiation 6 is preferably provided aspulsed radiation by the laser source 5. The scanner 8 has a two-partdesign in the construction of FIG. 3 and consists of an xy-scanner 8 a,which is realized, in one variant, by two galvanometer mirrors withsubstantially orthogonal deflection. The scanner 8 a two-dimensionallydeflects the laser beam 6 coming from the laser source 5, so that adeflected laser beam 20 is present downstream of the scanner 8. Thus,the scanner 8 a causes shifting of the position of the focus 19substantially perpendicular to the main direction of incidence of thelaser beam 6 in the cornea 17. For shifting of the depth position, az-scanner 8 b, preferably in the form of an adjustable telescope, forexample, is provided in addition to the xy-scanner 8 a in the scanner 8.The z-scanner 8 b ensures that the z-position of the focus 19, i.e. itsposition along the optical axis of incidence, is changed. The z-scanner8 b may be arranged preceding or following the xy-scanner 8 a.

It is not essential for the functional principle of the treatmentapparatus 1 how the individual coordinates are assigned to the spatialdirections nor that deflection by the scanner 8 a is effected alongmutually orthogonal axes. On the contrary, any scanner may be used whichcan shift the focus 19 in a plane in which the axis of incidence of theoptical radiation is not located. Further, any non-Cartesian coordinatesystems whatsoever can be used for deflection or control of the positionof the focus 19. Examples include spherical coordinates or cylindricalcoordinates.

The position of the focus 19 is controlled by the scanners 8 a, 8 bunder the control of the control device 11, which performs suitablesettings of the laser source 5, of the modulator 9 (not shown in FIG. 3)as well as of the scanner 8. The control device 11 ensures suitableoperation of the laser source 5 as well as the three-dimensional focusshift described here as an example, thus finally producing a cut surfacewhich isolates a determined corneal volume that is to be removed forcorrection of refraction.

The control device 11 works according to predetermined control data,which are predefined, for example, in the laser device 4 described heremerely as an example, as target points for focus shifting. The controldata are usually compiled in a control dataset, which providesgeometrical parameters for the cut surface to be formed, e.g. thecoordinates of the target points as a pattern. In this embodiment, thecontrol dataset then also includes concrete set values for the focusposition shifting mechanism, e.g. for the scanner 8.

FIG. 4 shows an example of how to produce the cut surface using thetreatment apparatus 1. A corneal volume 21 is isolated in the cornea 17by shifting the focus 19, into which the focused beam 7 is bundled. Forthis purpose, cut surfaces are formed, which are provided here, by wayof example, as an anterior flap cut surface 22 as well as a posteriorlenticle cut surface 23. These terms are to be understood here merely asexamples and are intended to establish a relation to the conventionalLASIK or FLEX methods, for which the treatment apparatus 1 is provided,as already described. It is only essential here that the cut surfaces 22and 23 as well as peripheral cuts, which are not referred to in detailand which make the cut surfaces 22 and 23 converge at their peripheries,isolate the corneal volume 21. By means of an opening cut 24, a corneallamella anteriorly limiting the corneal volume 21 can further be foldedaside so as to allow removal of the corneal volume 21.

FIG. 5 schematically shows the treatment apparatus 1, by reference towhich the planning device 16 shall be explained in more detail. In thisvariant, the treatment apparatus 1 comprises at least two devices ormodules. The laser device 4 already described emits the laser beam 6onto the eye 2. As already described, operation of the laser device 4 iseffected fully automatically by the control device 11, i.e., the laserdevice 4 starts generating and deflecting the laser beam 6 in responseto a corresponding start signal and, thus, generates cut surfaces, whichare structured as described, in order to remove the corneal volume 21.The laser device 5 receives the control signals required for operationfrom the control device 11, to which corresponding control data havebeen provided before. This is effected by the planning device 16, whichis shown in FIG. 6 merely by way of example, as part of the controldevice 11. Of course, the planning device 16 may also be providedseparately and may communicate with the control device 11 either in awire-bound or wireless manner. It is then only essential to provide acorresponding data transmission channel between the planning device 16and the control device 11.

The planning device 16 generates a control dataset which is provided tothe control device 11 to carry out the ophthalmic correction ofrefraction. In doing so, the planning device uses measurement datarelating to the cornea of the eye. In the presently describedembodiment, these data come from a measurement device 28, which haspreviously measured the eye 2 of the patient 2. Of course, themeasurement device 28 may have any design whatsoever and may transmitthe corresponding data to the interface 29 of the planning device 16.

Now, the planning device assists the user of the treatment apparatus 1in defining the cut surface for isolation of the corneal volume 21. Thismay even include a fully automatic definition of the cut surfaces, whichmay be effected, for example, by the planning device 16 using themeasurement data to determine the corneal volume 21 to be removed, whoseboundary surfaces are defined as cut surfaces, and generating therefromsuitable control data for the control device 11. At the other end of thedegree of automation, the planning device 16 may provide input means bywhich a user inputs the cut surfaces in the form of geometricalparameters, etc. Intermediate steps provide suggestions for the cutsurfaces, which the planning device 16 generates automatically and whichcan then be modified by an operator. Basically, all the concepts alreadyexplained in the above, more generic part of the description, can beapplied here in the planning device 16.

In order to perform a re-treatment, the planning device 16 generatescontrol data for cut surface production, which are then used in thetreatment apparatus 1. FIG. 6 shows an example of the possible locationof the cut surfaces, wherein the cut surfaces corresponding to those ofFIG. 4 bear the same reference symbols. Now, the essential difference tothe situation of FIG. 4 is that there already is an older cut 30 in thecornea 17, which cut resulted from a previous operation, e.g. from anoperation according to the FLEX method. In FIG. 6 as well as in thesubsequent figures, the older cut 30 is indicated by a dot and dashline. For distinction from the older cut 30, the cut surfaces intendedfor re-treatment are indicated by a dashed line.

As FIG. 6 shows, the control data are defined such that the re-treatmentcut surfaces eliminating the residual need for correction are alllocated beneath the older cut 30. Thus, with respect to the older cut30, the corneal volume 21 to be removed is generated posteriorly, forexample by a lenticle cut 23 and by a flap cut 22, including a lateralopening cut 24. This avoids any undesired interference with the oldercut 30.

In a modification (not shown) of the cut surfaces of FIG. 6, all the cutsurfaces provided or used for re-treatment may also be located withinthe corneal lamella 31 which has been generated between the older cut 30and the anterior surface of the cornea 17.

FIG. 7 shows a further variant which is applicable, in particular, ifthere is no sufficiently exact knowledge about the extent to which theolder cuts were carried out. The re-treatment cut surface, e.g.comprising a lenticle cut 23 and a flap cut 22, is now defined such thatthe older cuts 30 (again indicated by a dot and dash line) are locatedcompletely within the corneal volume 21 being removed for correction.This approach has the advantage that the number of boundary surfacesremaining in the cornea after the operation is small.

FIG. 8 shows a possibility which is applicable, in particular, if thepositions of the older cuts are particularly well known. There-treatment cut surfaces are then provided as continuations of theolder cut 30. This is applicable, of course, where the previousoperation was unintentionally terminated.

A further method of using older cuts is shown in FIG. 9, wherein thecorneal volume 21 to be isolated is defined by both older cuts 30 andcut surfaces produced during re-treatment. As an example, the use of theolder cut 30 as a flap cut is shown here, which is supplemented by alenticle cut 23 generated in the re-treatment. This is to be understoodas an example, of course, and it is also possible to use a cut extendinginto the lamella 31 as a supplement in the re-treatment.

In addition, it should also be noted that the treatment apparatus 1 orthe planning device 16, respectively, also specifically realizes themethod which was generally explained above.

A further embodiment of the planning device exists in the form of acomputer program or of a corresponding data carrier comprising acomputer program and realizing the planning device on a suitablecomputer so that the measurement data or the transplantation materialdata are input to the computer by suitable data transmission means andthe control data are transmitted from this computer to the controldevice 11, for which purpose data transmission means known to the personskilled in the art are, in turn, suitable.

1. A system for performing ophthalmic surgery in tissue of an eye afterat least one previous ophthalmic surgery in the tissue, comprising: atreatment apparatus comprising a laser device configured to generate atleast one cut surface in the tissue by deflecting a laser beam in theeye; a planning station configured to: access information on at leastone pre-operative cut generated in the at least one previous ophthalmicsurgery; define a cut surface on a basis of the information on the atleast one pre-operative cut; generate a control dataset describing thecut surface in terms of treatment apparatus control, and transmit thecontrol dataset to the treatment apparatus, wherein the laser devicecomprises a laser source emitting the laser beam as a pulsed laser beamhaving a pulse duration in a range of between 1 fs and 10 ps.
 21. 2. Thesystem as claimed in claim 1, wherein the laser beam has a pulse energyof between 0.01 μJ and 0.01 mJ.
 3. The system according to claim 1,wherein the tissue of the eye is a cornea and the planning station isconfigured to define the cut surface to confine corneal volume which isto be removed to correct a refraction error of the eye.
 4. The systemaccording to claim 1, wherein said planning station is configured togenerate the control dataset for a re-treatment of the previousophthalmic surgery which left the at least one pre-operative cut in thetissue.
 5. The system as claimed in claim 4, wherein the cut surfacecontinues the at least one pre-operative cut.
 6. The system of claim 1,further comprising at least one of the following measurement devices:OCT, refractometer, keratometer, abberometer, and wave-front measurementdevice, which in particular generates the information on the at leastone pre-operative cut generated in the at least one previous ophthalmicsurgery.
 7. The system as claimed in claim 1, wherein the tissue of theeye is a cornea and the cut surface comprises an opening cut leading toan anterior surface of the cornea.
 8. The system as claimed in claim 1,wherein the cut surface confines defective material of a cornea whichmaterial is to be removed.